1. Field of the Invention
The present invention relates to a patterning method of an organic electroluminescent (hereinafter referred to as organic EL) device in which ultraviolet ray is irradiated to an organic EL device to form a light-emission pattern.
2. Description of the Related Art
An organic EL device is a self-emitting type device employing an organic compound as a luminescent material. It can emit light with high speed, so that it is suitable for a display of a moving image. Further, an organic EL device has a characteristic that its device structure is simple, which makes it possible to reduce a size of a display panel. Since the organic EL device has such an excellent characteristic, it has been spreading in daily life for use in a cellular phone, or a vehicle-mounted display.
There has conventionally been a method of coloring a cathode layer with the use of a mask, or a method of insulation using a resist, as a method for patterning the organic EL device.
However, these methods entail problems as follows. Specifically, a pattern blurring of a cathode occurs due to the deviation of the mask, or the like. Further, appropriate solvent corresponding to the organic luminescent material should be selected, since the method includes a wet-type photolithography process.
The term “pattern” here indicates an icon, character, letter, illustration, graphic, design, or the like displayed on a device panel, and the term “patterning” means providing the function for displaying these patterns.
In the conventional patterning method, it is difficult to cope with high definition of the pattern. Therefore, various studies have been made for amore efficient patterning method. For example, Japanese Patent No. 2793373 proposes, as one method of efficiently patterning with high definition, a patterning method in which ultraviolet ray is irradiated to an organic EL device and the irradiated area is made a non-emission area.
In the patterning method disclosed in Japanese Patent No. 2793373, ultraviolet ray is irradiated to an organic EL device before or after an electrode is formed. When ultraviolet ray is irradiated after a panel is formed, transmittance of the ultraviolet ray at a transparent substrate and a transparent electrode is insufficient, so that sufficient effect of the irradiation of ultraviolet ray cannot be obtained. Therefore, it is difficult to efficiently perform patterning with high definition.
In this patterning method, the area of the EL device where ultraviolet ray is irradiated is made a non-emission area, resulting in that the contrast in the emission area cannot be controlled.